Molybdenum-containing composition

ABSTRACT

A reactive composition comprising:
         (A) a glycerol monoester; (B) an acid amide in which the chain length of the acid portion comprising the amide contains about 8 to about 28 carbon atoms; and (C) a molybdenum compound in which the oxidation state of the molybdenum is +6; and a product prepared by reacting the reactive composition, including a product in the form of a composition which is useful as a friction modifier; and a lubricating composition comprising a lubricant in admixture with the friction modifier.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of International Application Number PCT/US2013/055751, filed Aug. 20, 2013, which claims priority to U.S. Provisional Application No. 61/684,963, filed Aug. 20, 2012.

FIELD OF THE INVENTION

The present invention relates to a molybdenum-containing composition which can be used in various types of applications. Initially, the present invention is described in connection with the use of the composition as an additive in admixture with a lubricating oil in which it functions as a friction modifier; the composition has, however, other uses as described hereinafter.

Friction modifiers, for example, in the form of a particular compound or in admixture with other compounds, are well known as additives which are included in lubricants and which function to improve the lubricating properties of the lubricant, for example, a motor oil. A lubricant is itself a material which upon application to a surface functions to reduce friction between moving surfaces. It is beneficial to reduce such friction for a variety of reasons, including the reduction of heat generation, of surface fatigue, and of the formation of “wear particles” which have an adverse effect on the surfaces being lubricated, typically metallic surfaces.

The prior art discloses many types of compounds which function as friction modifiers, including compounds which contain both molybdenum (Mo) and sulfur (S). There are views that support the notion that a Mo-containing compound must contain also S for the compound to function effectively as a friction modifier. There are, however, disadvantages associated with the use of a Mo and S-containing compound. For example, it has been reported that lubricants containing such compounds cause corrosion of metal surfaces lubricated therewith; also, there are various Mo- and S-containing compounds that are insoluble in lubricating oils to the extent that their effectiveness as a friction modifier is affected adversely.

The present invention relates to the provision of a composition which includes Mo, including a Mo-containing composition which does not require the presence of S in order to function effectively and efficiently as a friction modifier.

SUMMARY OF THE INVENTION

The present invention includes the provision of a reactive composition comprising:

(A) a glycerol monoester (GMO), preferably about 35 to about 65 wt. % of the monoester;

(B) an acid amide in which the chain length of the acid portion comprising the amide contains about 8 to about 28 carbon atoms, preferably about 15 to about 45 wt. % of the acid amide; and

(C) a molybdenum compound in which the oxidation state of the molybdenum is +6 (hereafter for convenience “Mo+6”), preferably about 5 to about 25 wt. % of the molybdenum compound.

Unless stated otherwise, as used herein, “wt. %” means percent by weight based on the total weight of the composition.

The present invention includes also a product prepared by reacting a reactive composition as described hereinabove.

In addition, the present invention includes the provision of a product in the form of a composition which is useful as a friction modifier and which comprises a mixture of the following:

(A) a compound prepared by reacting a Mo+6 (hereafter “a Mo reactant”) with an acid amide in which the chain length of the acid portion comprising the amide contains about 8 to about 28 carbon atoms (hereafter “an acid amide”), the compound hereof comprising preferably about 25 to about 60 wt. % of the mixture;

(B) a compound prepared by reacting a Mo reactant with a glycerol monoester, the compound hereof comprising preferably about 25 to about 40 wt. % of the mixture; and

(C) a compound prepared by reacting a Mo reactant, an acid amide, and a glycerol monoester, the compound hereof comprising preferably about 10 to about 25 wt. % of the mixture.

Another aspect of the present invention is the provision of a method which comprises:

(A) heating a mixture of the following compounds:

-   -   (i) a glycerol monoester, preferably about 35 to about 65 wt. %         of the mixture;     -   (ii) an acid amide, preferably about 15 to about 45 wt. % of the         mixture; and     -   (iii) a Mo reactant, preferably about 5 to about 25 wt. % of the         mixture; and including heating the mixture under temperature,         time, and other conditions which are sufficient to produce a         composition in the form of a reaction product that comprises a         Mo+6 complexed with GMO or with an acid amide or with GMO and an         acid amide. The product is typically a viscous homogeneous         liquid.

An additional aspect of the present invention is the provision of a lubricating composition, preferably a composition comprising a lubricating oil, in admixture with an additive which comprises a product that is described hereinabove and that has the properties of a friction modifier. In preferred form, the lubricating composition comprises about 0.1 to about 1 wt. % of the additive.

There are various beneficial aspects associated with the provision of the present invention; for example, consider the following. A friction modifier within the scope of the present invention has the ability to improve the lubricating properties of a lubricant by at least about 0.3 wt. %. According to industry standards, such improvement is measured by frictional properties using instruments such as a High Frequency Reciprocating Rig (HFRR) and a Mini Traction Machine (MTM). Such improvement can be achieved without the use of sulfur; accordingly, in preferred form, the friction modifier contains no sulfur or is substantially sulfur-free, that is, contains no greater than about 0.01 wt. % of sulfur. Friction modifiers within the scope of the present invention are soluble in many types of popularly used lubricants and are also compatible with many types of popularly used additives that are used in lubricating compositions. For example, the present invention includes within its scope lubricating compositions which contain a friction modifier of the present invention and which are precipitate- and haze-free, including compositions which contain also additives which function to improve properties of the lubricating composition. The nature of a composition comprising a friction modifier hereof is such that, relative to other Mo-containing friction modifiers, friction modifiers within the scope of the present invention can include higher amounts of Mo than such other modifiers.

DETAILED DESCRIPTION OF THE INVENTION

The present invention encompasses within its scope a composition which can be prepared from a reactive mixture which includes: (A) a glycerol monoester; (B) an acid amide in which the chain length of the acid portion of the amide contains about 8 to 28 carbon atoms (hereafter for convenience referred to as “the acid amide”); and (C) Mo+6. There follows a description of the aforementioned reactants of the reactive mixture.

A glycerol monoester comprises a compound in which one of the hydroxyl groups of glycerol (1,2,3-propane triol) is esterfied with an acid, typically a fatty acid. The chain length of the fatty acid can vary, for example: a short chain length of fewer than six carbon atoms; a medium chain length of six to 12 carbon atoms; and a long chain length of more than 12 carbon atoms, for example, up to about 22 carbon atoms. The fatty acid can be saturated or unsaturated, including those which have one double bond between carbon atoms (monounsaturated) and those having more than one double bond between carbon atoms (polyunsaturated).

The following are examples of saturated fatty acids that can comprise the ester portion of the glycerol monoester: butyric, caprylic, capric, lauric, myristic, palmitic, stearic, and arachedic. The following are examples of unsaturated fatty acids that can comprise the ester portion of the glycerol monoester: myristoleic, palmitoleic, sapienic, oleic, vaccenic, linoleic, and linolenic.

In preferred form, the fatty acids that comprise the ester portion of the glycerol monoester have a chain length of about 14 to about 22 carbon atoms and are monounsaturated. Particularly preferred fatty acids are oleic and lauric which are high in alpha mono content, for example, at least about 52 wt. % thereof, and which have a low content of free glycerine, for example, no greater than about 70 wt. % thereof.

The acid amide used in the practice of the present invention can be a primary, secondary, or tertiary amide. A primary acid amide has the basic structure of

wherein R represents the residue of an acid, typically a fatty acid. In a secondary acid amide, one of the hydrogen atoms pictured in Formula 1 above has in its place an alkyl group in which none of its carbon(s) is substituted or in which one or more of its carbons include one or more substituents. In a tertiary acid amide, both hydrogens atoms have in their place alkyl groups which may be the same or different, with neither of the alkyl groups containing a substituent or with one or more of the carbons of each alkyl group including one or more substituents.

The acid portion of the acid amide is the residue of a carboxylic acid, typically a fatty acid, that has a chain length of about 8 to about 28 carbon atoms. The fatty acid can be saturated or unsaturated, including, for example, those having one double bond between carbon atoms (monounsaturated).

The following are examples of saturated fatty acids that can comprise the acid portion of the amide: caprylic, capric, lauric, myristic, palmitic, stearic, arachedic, and cerotic. The following are examples of unsaturated fatty acids that can comprise the acid portion of the amide: myristoleic, palmitoleic, sapienic, oleic, vaccenic, linoleic, linolenic, and erucic.

In preferred form, the fatty acids that comprise the acid portion of the acid amide have a chain length of about 14 to about 22 carbon atoms and are monounsaturated.

Overall, the preferred form of the acid amide is a secondary or tertiary amide, the preferred acid residue of the amide is that of oleic or lauric acid, and the preferred alkyl group of the secondary or tertiary amide is that of a hydroxyalkyl having up to about four carbon atoms.

Particularly preferred acid amides are N,N-bis(2-hydroxyethyl) oleamide and N,N-bis(2-hydroxyethyl) cocoamide.

The molybdenum compound for use in the practice of the present invention includes a compound in which the oxidation state of molybdenum is +6, for example, molybdenum trioxide, molybdenum hexachloride, and ammonium molybdate. At about 18° C., molybdenum trioxide is a crystalline solid which is slightly soluble in water; it melts at about 795° C. At room temperature, molybdenum hexachloride is a solid which melts at 254° C. Ammonium molybdate having a formula of (NH₄)₂ MoO₄) or of (NH₄)₆Mo₇0₂₄ can be used. For use in the practice of the present invention, molybdenum trioxide is preferred.

The product of reaction is presumed to be a reaction product of Mo bound to the OH groups of the glycerol monoester, for example, of glycerol monooleate, and nitrogen atoms of the amide. Glycerol monoester is present in excess to drive the reaction to completion. In an exemplary reaction mixture, the weight percents of glycerol monooleate, molybdenum trioxide and oleyl amide are respectively about 42%, about 9% and about 35%. The mixture of reactants is heated initially at a temperature and for a time in order to initiate and speed the reaction; thereafter the temperature can be raised and the mixture heated for a time in order to distill out of the reaction mixture any excess solvent. For example, in reacting preferred reactants (for example, glycerol monoleate, molybdenum trioxide and N,N-bis(2-hydroxyethyl) oleamide), the mixture can be heated to about 70 to about 85° C. for about 2 hours, and then the temperature can be raised to about 95 to about 105° C. for an additional 2 hours. Addition of water and a solvent, for example, xylene, improves the yield by aiding in the dissolution of the Mo reactant as the reaction progresses. A final product with a water content of up to less than 0.8 wt. %, is exemplary. However, a water-free product or one that has a water content of no greater than about 0.3 wt. % has improved self-life, for example, precipitation of solids from the liquid product is lessened or eliminated.

The friction modifier of the present invention can be used with a variety of lubricants, including, for example, greases, engine oils, and metal working fluids. It is believed that it will be used widely in compositions in which the lubricant comprises a lubricating oil, the particular oil being selected on the basis of the involved lubricating application. Some examples of such oils include natural occurring oils, for example, base stocks API I, II, and III, and synthetic oils, for example, polyalphaolefin API IV and polyesterglycol API V.

With respect to greases, they are thixotropic semisolid lubricants with high initial viscosity that drops with shear. They can function as a sealant to minimize leakage and keep out contaminants. They are used typically in applications where frequent relubrication is difficult or undesirable such as, for example, for machines that run intermittently, for operations where the relubrication site is not easily accessible, for extreme operating conditions, and where lubricant oils will not stay in place. The following are examples of 6 general types of greases: mineral oils mixed with solid materials, heavy asphaltic-type oils, extreme-pressure greases, roll-neck greases, soap-thickened mineral oils, and multi-purpose greases. Most greases are used for lubricating bearings and the choice of grease depends on a number of factors including, for example, the nature of the substrate, application needs such as, for example, anti-friction, high load conditions, and operating temperatures.

The major function of the friction modifier of the present invention in grease is to provide reduction of friction and anti-wear properties. Generally speaking, greases are composed of a base oil (typically about 70-95 wt. %), thickener (about 3-30 wt. %), and additives (up to about wt. 10%) for oxidation and rust inhibition, extreme pressure, antiwear, and friction reduction.

The friction modifier should be used in an amount which improves the lubricating properties of the lubricant. Broadly, speaking and taking into account the various types of lubricants, the particular friction modifier used, and the various types of applications of use, it is believed that the friction modifier should comprise at least about 0.3 wt. % of the composition comprising the lubricant and additive. For most applications, it is believed that an amount of the friction modifier of up to about 1 wt. % will be satisfactory. For use with compositions comprising a lubricating oil, it is preferred that the friction modifier comprise about 0.5 to about 1 wt. % of the composition.

The present invention contemplates also the use of other additives in the composition comprising the lubricant and friction modifier. Additives are well known for use in such types of compositions and include, for example, dispersants, viscosity agents, antioxidants, stabilizers and antiwear agents. Speaking generally, the additives generally comprise about 20 wt. % to about 30 wt. % of the composition.

As mentioned above, a Mo-containing composition of the present invention can be used in applications other than those in which it is used in admixture with a lubricant to improve its lubricating properties. For example, it can be used as an antiwear additive. Zinc dithiophosphate (ZDDP) is used widely in engine oils as an antiwear and antioxidant additive and contains phosphorous and sulfur which is detrimental to catalytic converters. When sulfur-free, Mo-containing additives are used in combination with ZDDP, the total amount of phosphorous and sulfur can be reduced.

EXAMPLES

The following examples are illustrative of particular embodiments of the present invention. The compositions which are the subject of Example Nos. 1 and 2 are useful as friction modifiers.

Example No. 1

This example is illustrative of the preparation of a friction modifier prepared from: (a) glycerol monooleate (hereafter “GMO”—at room temperature, 20 to 25° C., a solid which melts at about 35 to 37° C.); (b) N, N-bis(2-hydroxyethyl) oleamide (hereafter “oleamide”—at room temperature, a liquid which boils at about 150° C.); and (c) molybdenum trioxide (hereafter “MoO₃”—at room temperature, a solid which melts at 795° C.).

Solid GMO is pre-heated in an oven at 50° C. for 30 minutes to its liquid form. There are added to a 1-liter flask 180 g liquid GMO and 150 g of liquid oleamide to form a liquid mixture thereof. Forty g of solid Mo0₃ in the form of a powder are added to the liquid mixture and stirred therein to form a liquid in which the Mo0₃ solids are dispersed. Xylene and a small amount of water are added as additional reagents to the dispersion to promote reaction through improved solubility of the reactants and to improve the solubility of the product of reaction. The resulting reactive mixture is heated with stirring at 70-75° C. under nitrogen purge for about 4 hours. The color of the mixture changes from a gray color at the beginning of the reaction to a milky brown, and then to a dark brown. The mixture is then heated to 100-110° C. to evaporate water. The final product amounts to 352 g, is a dark brown viscous liquid, and is completely soluble with commercially available engine oils.

Example No. 2

This example is like that of Example No. 1 except that the amount of water in the final product is about 0.3 wt. % and also the GMO constituent is replaced by glycerol monolaurate (hereafter “GML”—at room temperature, a pasty substance having a melting point of 23 to 27° C.). The amount of reagents and conditions of reaction are the same as those described in Example No. 1.

The color of the mixture changes from a gray color at the beginning of the reaction to a milky green, and then to dark green. After heating the mixture to 100-110° C., 358 g of a soft solid product which is compatible with most commercially available engine oils are obtained.

Selected physical properties of the products of Example Nos. 1 and 2 are measured. The amount of water is measured using the Karl Fisher titration method. Acid values are measured through KOH titration pursuant to ASTM D664. Viscosities at 40° C. and 100° C. are measured using a Brookfield viscometer. The properties are reported in Table 1 below.

TABLE 1 Physical Properties/Compositions of Example Nos. 1 and 2 Viscosity Viscosity @4° C., @100° C., Acid Water Solubility in Composition cp cp Number content Appearance Oil Ex. No. 1 1332 48 52 <0.8% Dark brown No haze Ex. No. 2 353 19.2 28 about Dark green No haze 0.3%

Evaluation of Composition of Example No. 1 as a Friction Modifier

There is evaluated the coefficient of friction (hereafter “COF”—both boundary and mixed thin film) of a base lubricating oil containing, as an additive, the composition prepared by the process of Example No. 1. The evaluation includes testing by use of a High Frequency Reciprocate Rig (hereafter “HFRR”) at Intertek Automotive Research, Inc. and of a Mini-Traction Machine (hereafter “MTM”) at Powertrib Lab, Inc. The procedure for HFRR is based on ASTM D6079. The testing at Powertrib Lab involved the use of a modified MTM procedure based on Jonston, et al., “Tribology Tractions, 34(2), 187, 1991” to measure mixed friction and film thickness. The base lubricating oil is a fully formulated SAE 5W20 that contains 0.5 wt. % of the composition of Example No. 1. For comparative purposes, a commercially available friction modifier (glycerol monooleate+GMO) is evaluated also.

Friction data are collected to simulate real engine running conditions which include variation in temperature, speed, and load.

The results of the evaluations of boundary friction measured at various conditions by HFRR are shown in the graph below.

Comparing the commercial GMO friction modifier with the friction modifier of the present invention shows that the latter provides at least a 20% improvement in terms of friction reduction at 120° C. and higher temperatures. The 120° C. temperature is equivalent to that of the running condition of normal engine. The lower the friction between metal parts in the engine, the better the fuel economy.

MTM friction data, stribek curves, film thickness and wear are measured against different sliding speeds, loads, initial and prolonged rubbing, and temperatures. Results suggest that friction modifiers within the scope of the present invention reduce both boundary and mixed friction and that films formed therefrom on metal surfaces are very stable and stay intact after prolonged rubbing. The use of such friction modifiers in engine oil improves fuel economy.

With respect to the composition of Example No. 2, that is, the GML-based composition which is a soft solid, it can be used effectively as a friction modifier for metal working and grease applications. 

1. A reactive composition comprising: (A) a glycerol monoester (GMO); (B) an acid amide in which the chain length of the acid portion comprising the amide contains about 8 to about 28 carbon atoms; and (C) a molybdenum compound in which the oxidation state of the molybdenum is +6 (hereafter “a Mo reactant”).
 2. A composition according to claim 1 comprising about 35 to about 65 wt. % of the monoester; about 15 to about 45 wt. % of the acid amide; and about 5 to about 25 wt. % of the molybdenum compound.
 3. A product prepared by reacting a reactive composition according to claim
 1. 4. A product prepared by reacting a reactive composition according to claim
 2. 5. A product in the form of a composition which is useful as a friction modifier and which comprises a mixture of the following: (A) about 25 to about 40 wt. % of a compound prepared by reacting a Mo reactant with an acid amide in which the chain length of the acid portion comprising the amide contains about 8 to about 28 carbon atoms (hereafter “an acid amide”); (B) about 25 to about 40 wt. % of a compound prepared by reacting a Mo reactant with a glycerol monoester; and (C) about 10 to about 25 wt. % of a compound prepared by reacting a Mo reactant, an acid amide, and a glycerol monoester.
 6. A product according to claim 5 wherein the compound of (C) above is prepared by reacting about 5 to about 25 wt. % of the Mo reactant, about 15 to about 45 wt. % of the acid amide; and about 35 to about 65 wt. % of the monoester.
 7. A composition according to claim 1 wherein the composition contains no sulfur or contains no greater than about 0.01 wt. % of sulfur.
 8. A composition according to claim 2 wherein the composition contains no sulfur or contains no greater than about 0.01 wt. % of sulfur.
 9. A product according to claim 5 wherein the composition contains no sulfur or contains no greater than about 0.01 wt. % of sulfur.
 10. A composition according to claim 2 in which the molybdenum compound includes molybdenum trioxide, molybdenum hexachloride, or ammonium molybdate.
 11. A composition according to claim 10 including molybdenum trioxide.
 12. A composition according to claim 2 wherein the glycerol monoester is a compound in which one of the hydroxyl groups of glycerol is esterfied with a fatty acid which has a chain length of about 14 to about 22 carbon atoms and which can be saturated or unsaturated.
 13. A composition according to claim 12 wherein the fatty acid is oleic acid or lauric acid.
 14. A composition according to claim 2 wherein the amide is the residue of a fatty acid which has a chain length of about 14 to about 22 carbon atoms and which is monounsaturated and the amide being a secondary or tertiary amide having an alkyl group(s) in which one or more of the carbon atoms thereof is substituted with a hydroxyl group.
 15. A composition according to claim 14 wherein the amide is N,N-bis(2-hydroxyethyl) oleamide or N,N-bis(2-hydroxyethyl) cocomide.
 16. A product according to claim 5 wherein the compound of (C) is prepared by reacting about 5 to about 25 wt. % of the Mo reactant, about 15 to about 45 wt. % of the acid amide, and about 35 to about 65 wt. % of the monoester; and wherein the glycerol ester of the compound of (B) is a compound in which one of the hydroxyl groups of glycerol is esterfied with a fatty acid which has a chain length of about 14 to about 22 carbon atoms and which can be saturated or unsaturated; and wherein the acid amide of the compound of (A) is the residue of a fatty acid which has a chain length of about 14 to about 22 carbon atoms and which is monounsaturated and the amide being a secondary or tertiary amide having an alkyl group(s) in which one or more of the carbon atoms thereof is substituted with a hydroxyl group.
 17. A product according to claim 5 wherein the Mo reactant includes molybdenum trioxide, molybdenum hexachloride, or ammonium molybdate.
 18. A product according to claim 17 wherein the Mo reactant includes molybdenum trioxide.
 19. A product, according to claim 5 wherein the glycerol monoester is a compound in which one of the hydroxyl groups of glycerol is esterfied with a fatty acid which has a chain length of about 14 to about 22 carbon atoms and which can be saturated or unsaturated.
 20. A product according to claim 19 wherein the fatty acid includes oleic acid or lauric acid.
 21. A product according to claim 5, wherein the amide is the residue of a fatty acid which has a chain length of about 14 to about 22 carbon atoms and which is monounsaturated, the amide being a secondary or tertiary amide having an alkyl group(s) in which one or more of the carbon atoms thereof is substituted with a hydroxyl group.
 22. A product according to claim 21 and wherein the amide includes N,N-bis(2-hydroxyethyl) oleamide or N,N-bis(2-hydroxyethyl) cocomide.
 23. A method which comprises: (A) heating a reactive mixture of the following compounds: (i) a glycerol monoester, (GMO); (ii) an acid amide; and (iii) a Mo reactant (Mo+6); and including heating the mixture under temperature, time, and other conditions which are sufficient to produce a composition in the form of a reaction product that comprises a Mo+6 complexed with GMO or with an acid amide or with GMO and an acid amide.
 24. A product prepared by the method of claim
 23. 25. A lubricating composition comprising a lubricant in admixture with a friction modifier additive which comprises a product according to claim 5 in an amount which improves the lubricating properties of the lubricant.
 26. A lubricating composition comprising a lubricant in admixture with a friction modifier additive which comprises a product according to claim 5, wherein the lubricating composition comprises up to about 1 wt. % of the additive.
 27. A composition according to claim 26 wherein the lubricating composition comprises a lubricating oil and about 0.5 to about 1 wt. % of the additive.
 28. A composition according to claim 26 wherein the additive contains no sulfur or contains no greater than about 0.01 wt. % of sulfur.
 29. A composition according to claim 26 wherein the lubricant comprises a grease, an engine oil, or a metal working fluid.
 30. A composition according to claim 29 wherein the lubricant is a grease. 